1. Use a soft tape measure or a piece of string.
  2. Place it around your head, positioned mid-forehead and just above the ears.
  3. If you are using a tape measure, read the measurement where the end crosses the main part of the tape.
  4. If you used string, mark the string where the main part crosses the end.  Measure from the end to the mark using a standard tape measure.
  5. Measure in centimetres.